1. Field of the Invention
The present invention relates to a sustained release drug carrier, and more particularly to a sustained release drug carrier suitable for medical use.
2. Description of the Prior Art
Hydroxyapatite, which is a calcium phosphate-based ceramic, has structure similar to inorganic components of the bone. For this reason, hydroxyapatite has excellent biocompatibility and is used for various biocompatible materials such as artificial dental implants, bone replacement materials, dental cements, and the like.
In clinical practice, hydroxyapatite is used by being formed into dense articles, granular articles, porous articles having arbitrary porosity, and the like.
As for examples of such clinical applications of the hydroxyapatite, sustained release drug carriers which are formed of calcium phosphate-based ceramic and which carry sustained release drug can be mentioned. These sustained release drug carriers are capable of continuously releasing the drug into the body over long periods of time.
Using such a sustained release drug carrier makes it possible to maintain an effective drug concentration in a localized area of the body. This results in fewer side effects in comparison with systemic drug administration such as oral administration and parenteral administration. Therefore, treatments using such sustained release drug carriers draw attention as one of the effective therapeutic methods.
However, the above-described conventional sustained release drug carriers involve the following drawbacks.
A dense sustained release drug carrier has sufficient strength for an implant material or the like, but it is not possible to carry a sufficient amount of drug and release them in an adequate manner.
On the other hand, a porous sustained release drug carrier can adequately carry and release a drug, but it rapidly releases a large amount of drug in the initial release stage. In other words, prolonged release of the drug at constant rates is difficult to achieve.
Another drawback of a porous sustained release drug carrier is that it is difficult to give this carrier sufficient strength necessary for an implant material.
Therefore, it is an object of the present invention to provide a sustained release drug carrier whose drug release properties can be controlled and which is capable of exhibiting better drug release action suitable for the application sites, type of drugs to be carried, and the like.
Another object of the present invention is to provide a method for manufacturing such a sustained release drug carrier.
In order to achieve the above objects, the present invention is directed to a sustained release drug carrier comprising:
a ceramic composite which is formed by bonding a plurality of ceramic bodies together; and
drugs impregnated into the ceramic composite.
According to the present invention, it is possible to provide a sustained release drug carrier whose drug release properties can be controlled and which is capable of exhibiting better drug release action suitable for the application sites, type of drugs to be carried, and the like.
In this invention, it is preferred that the ceramic bodies have different porosities.
Further, in this invention, it is also preferred that at least one of the ceramic bodies has porosity of 5 to 90%.
Furthermore, in this invention, it is also preferred that the average pore size of at least one of the ceramic bodies lies within the range of 100 to 500 xcexcm.
Moreover, in this invention, it is also preferred that the pores include three-dimensionally communicating pores having capillaries. In this case, the average pore size of the capillaries preferably lies within the range of 0.1 to 20 xcexcm.
Still further, in this invention, it is also preferred that each of the ceramic bodies is formed from the same material.
Still further, in this invention, it is also preferred that at least one of the ceramic bodies is composed of a calcium phosphate-based compound. In this case, it is preferable that the calcium phosphate-based compound has a Ca/P ratio of 1.0 to 2.0. Preferably, the calcium phosphate-based compounds is hydroxyapatite.
Still further, in this invention, it is also preferred that the drugs include biologically active substances.
Still further, in this invention, it is also preferred that the ceramic composite is configured as a bone replacement material.
The present invention is also directed to a method of manufacturing a sustained release drug carrier, the method comprising the steps of:
preparing ceramic bodies to be bonded together, each of the ceramic bodies having a bonding surface;
preparing a slurry in which primary particles of a bonding ceramics are dispersed;
applying the slurry to the bonding surface of at least one of the ceramic bodies to be bonded;
sintering the ceramic bodies between which the slurry has been interposed to bond them together, to obtain a ceramic composite; and
impregnating a drug into the obtained ceramic composite.
In this invention, it is preferred that the bonding ceramics in the slurry is constituted from the same material as that of at least one of the ceramic bodies to be bonded.
Further, in this invention, it is also preferred that the bonding ceramics is composed of a calcium phosphate-based compound. In this case, the calcium phosphate-based compounds preferably include hydroxyapatite.
These and other objects, structures and advantages of the present invention will be apparent more clearly from the following description of the invention based on the examples.